The present invention is related to the development of a stable and high yield mint plant called xe2x80x98Damrooxe2x80x99 capable of producing viable seeds and phenotypically homogeneous seed derived population. More particularly, the invention relates to a high essential oil yielding variety xe2x80x98Damrooxe2x80x99 capable of producing viable seeds and therefore useful as a regular seed-source for raising homogenous seedling populations, an essential prelude to raising an ideal transplanted mint crop. The mint crop can be grown by transplantation after wheat cultivation, instead of cultivating it as main crop in place of wheat, a long sought wise option for cultivating mint without affecting the cultivation of the staple cereal wheat. xe2x80x98Damrooxe2x80x99 owing to its stability in seed-grown population for all morpho-physiological attributes, advances the development of sustained yields.
Menthol mint is grown in tropical and sub-tropical agro-climates for its essential oil. The oil, besides being widely used for producing menthol and the by-product dementholised oil (DMO), also finds uses in pharmaceutical and cosmetic industries. Menthol has a cooling, refreshing aroma and antiseptic properties. The menthol derivatives are also used in flavouring confectionery and cigarettes. Indeed, profitability in menthol mint is motivating the crop growers to grow it widely, even at the expense of conventional crops like wheat, sugarcane, and vegetables. This has been a metter of concern, especially regarding the fate of wheat crop in the Indogangetic plains of India. Wheat being a major staple food, significant reduction in wheat cultivation in exchange for cultivation of menthol mint may lead to the eventual wheat shortages. One pragmatic solution lies in the development of more efficient agrotechnologies for mint crops, so that crop growers would need only 50% of the area used presently and be able to cultivate both the crops. To the plant breeder, it means that he should put efforts to evolve varieties having doubled productivity. The Central Institute of Medicinal and Aromatic Plants (CIMAP), Lucknow, India, having made large efforts in this regard, has witnessed fascinating success in developing high yielding varieties with much impressive yield improvement, of which the variety xe2x80x98Kostixe2x80x99 (U.S. Ser. No. 09/145,546) having double oil productivity over earlier widely grown familiar variety xe2x80x98Shivalikxe2x80x99 (unpatented), is now enjoying the highest adorations of the crop growers.
Besides evolving the productive varieties, another wise option, which has long been proposed and initiated, but is yet to be much improved for its wide acceptance, is to resort to cultivating menthol mint as a late transplanted crop from April to July after wheat cultivation instead of cultivating it as major crop during February to June, when wheat is grown. In cultivating menthol mint as a transplanted crop, to depend upon the late planted sucker-grown nursery (but not seed-grown nursery) during the advent of summer (or spring) has been a general practice in raising transplanted mint crops during summer. However, with such a sucker-grown nursery exclusively providing the over matured hardy plants for transplanting, the plant growth as well as productivity in the transplanted mint crop, with very rare exceptions, are always very low. Seed-progeny research over the last five years has given an a priori clue that seeds can be grown in a nursery during winter months and young seedlings can be made available during summer months (April-May) for raising the transplanted mint crop. Keeping this in mind, attempts were made during 1994-1996 to extensively research into the open pollinated seed progenies of the familiar variety xe2x80x98Shivalikxe2x80x99 (unpatented) to explore the possibility of inventing a stable producing genotype.
The main object of the invention is to develop a stable and high yielding mint plant capable of producing viable seeds and phenotypically homogeneous seed derived plant population.
Another object of the invention is to identify and develop a stable seed-producing population variety of M. arvensis plant which, as generally known, does not set seeds under selfing conditions (except in very rare cases).
Yet another object of the invention is to develop plants that can provide homogeneous seeds even under cross pollination conditions within its own plant population.
Still another object is to develop mint plants capable of high yield of mint oil.
Another object of the invention is to develop a stable seed producing mint variety with high mint oil yield and menthol content.
Yet another object of the invention is to develop a novel mint variety that has improved disease resistance, higher biomass, high oil yield, and high seed yield.
To meet the above objectives, the present invention provides a novel Mentha arvensis mint population-variety xe2x80x98Damrooxe2x80x99 capable of producing viable seeds and phenotypically homogeneous seed-derived plant population when cross pollinated within its own population and capable of high yield of mint oil.
Accordingly, the invention provides a new and distinct variety xe2x80x98Damrooxe2x80x99 having the following new combination of characteristics as compared to conventional known varieties of M. arvensis, said plant having the following combination of characteristics:
(a) a plant height of about 100-110 cm;
(b) dark greenish leaves, whitish to whitish-purple flowers, and branching providing pyramidal habit;
(c) a high seed yield, compared to all other existing varieties of menthol mint;
(d) better tolerance to leaf spot, rust, and powdery mildew;
(e) a yield of essential oil containing 78-80% menthol and 12-17% isomenthone;
(f) a yield of seeds in the range of about 90-96 kg/hectare against 30 kg/hectare in xe2x80x98Shivalikxe2x80x99 (unpatented); and
(g) capable of retaining homogeneity in population for plant traits, despite out-crossing within the population.
In an embodiment, the invention also provides seeds produced by the novel plant xe2x80x98Damroo.xe2x80x99
In yet another embodiment, the invention provides progenies produced by the novel plant xe2x80x98Damroo.xe2x80x99
The seed producing variety xe2x80x98Damrooxe2x80x99 is the selection from the existing variety of mint plant called xe2x80x98Shivalikxe2x80x99 (unpatented).
The invention is described in detail herein below.